import sys
import pygame
from bullet import Bullet
from alien import Alien
from time import sleep


def check_keydown_events(event, settings, screen, ship, bullets):
    """
    按键按下
    """
    if event.key == pygame.K_UP:
        ship.moving_up = True

    elif event.key == pygame.K_DOWN:
        ship.moving_down = True

    elif event.key == pygame.K_LEFT:
        ship.moving_left = True

    elif event.key == pygame.K_RIGHT:
        ship.moving_right = True

    elif event.key == pygame.K_SPACE:
        fire_bullet(settings, screen, ship, bullets)

    elif event.key == pygame.K_q:
        sys.exit()


def check_keyup_events(event, ship):
    """
    按键松开
    """
    if event.key == pygame.K_UP:
        ship.moving_up = False

    elif event.key == pygame.K_DOWN:
        ship.moving_down = False

    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

    elif event.key == pygame.K_RIGHT:
        ship.moving_right = False


def check_events(settings, screen, stats, score_board, play_button, ship, aliens, bullets):
    """
    响应按键和鼠标事件
    """
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, settings, screen, ship, bullets)

        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)

        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(settings, screen, stats, score_board, play_button, ship, aliens, bullets, mouse_x,
                              mouse_y)


def check_play_button(settings, screen, stats, score_board, play_button, ship, aliens, bullets, mouse_x, mouse_y):
    """
    在玩家点击按钮Play时开始新游戏
    """
    if play_button.rect.collidepoint(mouse_x, mouse_y) and not stats.game_active:
        # 重置游戏设置
        settings.initialize_dynamic_settings()

        # 隐藏光标
        pygame.mouse.set_visible(False)

        # 重置游戏统计信息
        stats.reset_stats()
        stats.game_active = True

        # 重置记分牌图像
        score_board.prep_score()
        score_board.prep_high_score()
        score_board.prep_level()
        score_board.prep_ships()

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人，并让飞船居中
        create_fleet(settings, screen, ship, aliens)
        ship.center_ship()


def update_screen(settings, screen, stats, score_board, ship, aliens, bullets, play_button):
    """
    更新屏幕上的图案，并切换到最新屏幕
    """
    screen.fill(settings.screen_bg_color)

    # 在飞船和外星人之后重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()

    ship.blit_me()
    aliens.draw(screen)

    # 显示得分
    score_board.show_score()

    # 如果游戏处于非活动状态，就绘制Play按钮
    if not stats.game_active:
        play_button.draw_button()

    # 让最新绘制的屏幕可见
    pygame.display.flip()


def update_bullets(settings, screen, stats, score_board, ship, aliens, bullets):
    """
    更新子弹的位置，并删除已经消失的子弹
    """
    bullets.update()
    check_bullet_alien_collisions(settings, screen, stats, score_board, ship, aliens, bullets)

    # 删除已经消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom < 0:
            bullets.remove(bullet)


def check_bullet_alien_collisions(settings, screen, stats, score_board, ship, aliens, bullets):
    """
    相应子弹和外星人的碰撞情况
    """
    # 删除发生碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    if collisions:
        for aliens in collisions.values():
            stats.score += settings.alien_points * len(aliens)
            score_board.prep_score()
        check_high_score(stats, score_board)

    # 检查外星人是否被全部消灭，是则删除现有的子弹并新建一群外星人，并提高等级
    if len(aliens) == 0:
        bullets.empty()
        settings.increase_speed()

        # 提高等级
        stats.level += 1
        score_board.prep_level()

        create_fleet(settings, screen, ship, aliens)


def ship_hit(settings, screen, stats, score_board, ship, aliens, bullets):
    """
    响应飞船被外星人撞到
    """
    if stats.ship_number > 0:
        # 将ship_number减1
        stats.ship_number -= 1

        # 更新记分牌
        score_board.prep_ships()

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人，并将飞船放到屏幕底端中央
        create_fleet(settings, screen, ship, aliens)
        ship.center_ship()

        # 暂停
        sleep(0.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)


def update_aliens(settings, screen, stats, score_board, ship, aliens, bullets):
    """
    检查是否有外星人位于屏幕边缘，并更新所有外星人的位置
    """
    check_fleet_edges(settings, aliens)
    aliens.update()

    # 检测外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(settings, screen, stats, score_board, ship, aliens, bullets)

    # 检测外星人到达屏幕底端
    check_aliens_bottom(settings, screen, stats, score_board, ship, aliens, bullets)


def fire_bullet(settings, screen, ship, bullets):
    """
    如果还没有达到子弹数的限制，就发射一颗子弹
    """
    # 创建一颗子弹并加入到编组中
    if len(bullets) < settings.bullet_allowed:
        new_bullet = Bullet(settings, screen, ship)
        bullets.add(new_bullet)


def get_number_aliens_x(settings, alien_width):
    """
    计算每行可以容纳的外星人数量
    """
    available_space_x = settings.screen_width - 2 * alien_width
    return int(available_space_x / (2 * alien_width))


def create_alien(settings, screen, aliens, alien_number, row_number):
    """
    创建一个外星人并将其放在当前行
    """
    alien = Alien(settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def create_fleet(settings, screen, ship, aliens):
    """
    创建外星人群
    """
    # 创建一个外星人，并计算一行可以容纳的外星人个数
    # 假定外星人间距为外星人宽度
    alien = Alien(settings, screen)
    number_aliens_x = get_number_aliens_x(settings, alien.rect.width)
    number_rows = get_number_rows(settings, ship.rect.height, alien.rect.height)

    # 创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(settings, screen, aliens, alien_number, row_number)


def get_number_rows(settings, ship_height, alien_height):
    """
    计算屏幕可以容纳外星人的行数
    """
    available_space_y = (settings.screen_height - (3 * alien_height) - ship_height)
    return int(available_space_y / (2 * alien_height))


def check_fleet_edges(settings, aliens):
    """
    有外星人到达边缘时采取相应的措施
    """
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(settings, aliens)
            break


def change_fleet_direction(settings, aliens):
    """
    将外星人向下移动，并改变它们的方向
    """
    for alien in aliens.sprites():
        alien.rect.y += settings.alien_drop_speed
    settings.alien_fleet_direction *= -1


def check_aliens_bottom(settings, screen, stats, score_board, ship, aliens, bullets):
    """
    检测是否有外星人到达了屏幕底端
    """
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            ship_hit(settings, screen, stats, score_board, ship, aliens, bullets)
            break


def check_high_score(stats, score_board):
    """
    检查是否诞生了新的最高得分
    """
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        score_board.prep_high_score()
